Die for forging the cutting faces of rock drill bits



Aug. 22, 1944. s p, HUMPHREY 7 2,356,520

DIE FOR FORGING THE CUTTING FACES OF ROCK DRILL BITS Filed bet. 7, 1943. 2 Sheets-Sheet 1 1944. s. P. 'HUMPHREY 2,356,520

DIE FOR FORGING THE CUTTING FACES OF ROCK DRILL BITS Filed.0ot. 7, 1943 2 Sheets-Sheet 2 Patented Aug. 22, 1944 DIE FOR 'FORGING THE CUTTING FACES OF ROCK DRILL BITS Stephen Peter Humphrey, -Max Meadows, Va.

Application October 7, 1943, Serial No. 5053395 2 Claims.

This invention relates to dies for forming or renewing the cutting faces of rock drill bits, particularly rock drills having four cutting edges radiating from a common axis.

One of the objects of the invention isto p vide a two-part die'assemblage, including four cutters which by a single reciprocatory relative movement of the dies in a press, are forced together from different directions through the bit stock, severing the same by cutting off the old working face, and forming'a new face at the end of the stock.

Another object of the invention is to'provide a pair of dies each carrying a, butter in 'fixed position relative thereto, which cutters are movable with the dies from opposite directions toward one another along a common line of symmetry to a'position of point to point contact, anda pair of movable cutters-carried by one die on opposite sides of its fixed cutter, swingable responsive to the action of a cam carried bythe other die toward one another to a position of point topoint contact with the fixed cutters.

Another object of the invention is to provide a die construction as described, in which the movable cutters are normally spring retracted in a position to straddle-the bit stock upon the initial closing movement ofthe dies.

Other objects of the invention will appear as the following description of a preferred-and practical embodiment thereof proceeds.

In the drawings:

Figure 1 is a front elevation showing the bit face forming dies of 'th'esubject invention, set up in a press in separated relation, part of the press being omitted;

Figure 2 is a vertical cross-section in a plane passing through the common axis of contact of the cutters, showing the dies in closed position;

Figure 3 is a cross-section through the dies in a plane perpendicular to the common axis of the cutters, the latter being in closed position;

Figure 4 is a section taken along the line 4-4 of Figure 3;

Figure 5 is a perspective view of the working end of a drill bit, showing the nature of the face which the dies of the subject invention are adapted to produce.

Before referring specifically to the drawings, it may be stated that there are a number of known ways of renewing the worn and scarified working ends of drill bits, including filling and pressing, some of which expedients are carried out by means of dies or sharpening machines, but all of which are inordinately time-c nsum ng, and

at least for that reason, impractical; and that the present invention side-steps the shortcomings of the older methods by disregarding the old worn or-chipped working face and forging an entirely new face adjacent-thereto. This is done in a single and substantially instantaneous operation by cutting off the old 'face and producing a new face at the end of the bit stock. 7

"Referringnow in detail to the several figures, apairof cooperating dieblocks I and 2 are provided, these being shown in Figure 1, set upjin a conventional press 3, comprising a, fixed platen 4 and a movable head 5 suitably actuated as, for

example, by the pneumatically operated plunger 6.

The head is -guided by guide rods I, which are parallel to' the direction o'fmotion of the plunger, fixed to one of the die holding press members and slidable through guide apertures in theother.

The press has the'lower andupper jaws 8 and 9, each formedwith a buttress ledge II], the con- 'fronting faces of whichledges lie in planes performed by the overhanging clamping plates,

against the respective ledges.

The width of the bases of thedie blocks is slightly greater than the width of said channels, so that the die blocks blocks to any type of press. blocks are secured at one side in the press jaws may be firmly clamped. The shape and size of the bases of the die blocks is immaterial to the invention, and may be varied toadapt the die As shown, the die Band 9, indicating that other dies for other purposes, with which the invention may not be concerned, may be kept set up in the press without removing the die blocks I and 2.

Now, referring particularly to Figures 1, 2 and 3, the die blocks I and 2 are formed with interspective recesses, resting against the bottom walls I9 thereof, and being secured by the stud bolts 22. The inner ends of the fixed cutters are of tetrahedral shape, as shown, and symmetrical both as to their faces and edges with respect to a common line passing through their points parallel to the axis of the bit stock, and which line may be considered the axis of the dies.

One of the die blocks, for example, the die block 2, is provided with a pair of movable cutters 23 and 24, one on each side of the fixed cutter 2|, swingable laterally in transverse slots 25 formed intermediately in the side wall portions It and I! of the die block 2, and journaled on pivot pins 26 anchored in said side walls. The Working ends also of the movable cutters are of tetrahedral shape, and the movable cutters are so shaped and dimensioned that when they have been swung to fully closed position, their" I, is provided with cams 21 so situated on opposite sides of the fixed cutter 20 as to be contacted by the movable cutters 'upon the approach of the die blocks, and so shaped as to guide said movabl cutters inwardly at a uniform rate of ravel until they have reached closed position of contact with respect to the fixed guide members.

The movable cutters 23 and 24 are normally 7 held in retracted position by springs 28, so that they are able to straddle the bit stock in the initial relative approach movement of the die blocks until the movable cutters are engaged by the cams 21.

;In operation, the bit, which is to be re-faced, is first heated to the proper forging condition,

then-positionedadjacent its end between the open dies with' its axisapproximately in coincidence with the axis of the die, which is indicated by the point X in Figure 1, The press is then actuated to bring the dies together, forcibly closing the cutters through the bit stock, severing the terminal portion with the old working face,

;and simultaneously forging a new working face. The slight swell in the diameter of the bit stock incident to the displacement of metal by the cutters'is no detriment to a tool of this nature. The cutting face'produced by the: subject die tool is illustrated at 29 in Figure 5.

The bit'is then re-tempered in usual manner, and isready for use.

While I have in the above description disclosed what I believe to be a preferred and practical embodiment of the invention, it will be understood to those skilled in the art that the details of construction and arrangement of parts, as shown and described, are by way of illustration and not to be construed as limiting the scope of the invention as defined in the appended claims.

What I claim as my invention is:

lfDie tool for forging cutting faces on drill bits comprising a pair of cooperating die blocks adapted to be brought together in a press, a pair of similar cutters having tetrahedral cutting ends pivotally mounted in spaced relation on one block to swing into point to point contact, springs thrusting between said cutter and blocks to normally hold said cutters in retracted position, the other block having a pair of similar cams engageable by said cutters for causing them to move together responsive to the relative approach movement of said blocks, and a pair of cutters, fixed one with respect to each block having tetrahedral cutting faces similar to the cutting faces of said movable cutters positioned to be moved into point to point contact with one another and with the points of said movable cutters and with cutting edges in linear contact in a common plane intermediate the inner and outer faces of saidcutters, the faces and edges of the cutting ends of all of said cutters being symmetrical with respect to said plane and with respect to a line perpendicular to said plane passing through the common meeting point of the points of said. cutters.

2. Die tool for forging cutting faces on drill bits comprising a pair of cooperating die blocks adapted to be brought together in a press, a pair of similar cutters having tetrahedral cutting ends fixed one with respect to each block having tetra- STEPHEN PETER. HUMPI-IREY. 

